Alan Morris received his B.Sc. degree in geology from the Imperial College of Science and Technology in 1973 and his Ph.D. in geology from the University of Cambridge in 1980. He is a licensed professional geoscientist (geology) in the state of Texas. Before joining Southwest Research Institute in 2005, he was a full professor at the University of Texas at San Antonio, where he had been on the faculty for 22 years. Alan is now a staff scientist at Southwest Research Institute and focuses on quantitative analysis of deformation processes and stress in diverse tectonic regimes and conducts research and technical assistance projects for the oil industry.

Ronald McGinnis received his B.S. and M.S. degrees in geology from the University of Texas at San Antonio in 2002 and 2005, respectively. He is a senior research scientist at Southwest Research Institute. His work includes structural geological analysis of groundwater aquifers, characterization of faulted and fractured hydrocarbon reservoirs, and three-dimensional modeling of structurally complex hydrocarbon reservoirs and groundwater aquifers. In addition, he prepares and teaches training courses for the energy industry.

David Ferrill received his B.S. degree in geology from Georgia State University in 1984, his M.S. degree in geology from West Virginia University in 1987, and his Ph.D. in geology from the University of Alabama in 1991. He is a licensed professional geoscientist (geology) in the state of Texas. Before joining Southwest Research Institute in 1993, he was an exploration geologist at Shell Offshore Incorporated. David is now a director at Southwest Research Institute and performs geologic analyses, structural geologic consulting, and training for the oil and gas industry.

Alan Morris received his B.Sc. degree in geology from the Imperial College of Science and Technology in 1973 and his Ph.D. in geology from the University of Cambridge in 1980. He is a licensed professional geoscientist (geology) in the state of Texas. Before joining Southwest Research Institute in 2005, he was a full professor at the University of Texas at San Antonio, where he had been on the faculty for 22 years. Alan is now a staff scientist at Southwest Research Institute and focuses on quantitative analysis of deformation processes and stress in diverse tectonic regimes and conducts research and technical assistance projects for the oil industry.

Ronald McGinnis received his B.S. and M.S. degrees in geology from the University of Texas at San Antonio in 2002 and 2005, respectively. He is a senior research scientist at Southwest Research Institute. His work includes structural geological analysis of groundwater aquifers, characterization of faulted and fractured hydrocarbon reservoirs, and three-dimensional modeling of structurally complex hydrocarbon reservoirs and groundwater aquifers. In addition, he prepares and teaches training courses for the energy industry.

David Ferrill received his B.S. degree in geology from Georgia State University in 1984, his M.S. degree in geology from West Virginia University in 1987, and his Ph.D. in geology from the University of Alabama in 1991. He is a licensed professional geoscientist (geology) in the state of Texas. Before joining Southwest Research Institute in 1993, he was an exploration geologist at Shell Offshore Incorporated. David is now a director at Southwest Research Institute and performs geologic analyses, structural geologic consulting, and training for the oil and gas industry.

Alan Morris received his B.Sc. degree in geology from the Imperial College of Science and Technology in 1973 and his Ph.D. in geology from the University of Cambridge in 1980. He is a licensed professional geoscientist (geology) in the state of Texas. Before joining Southwest Research Institute in 2005, he was a full professor at the University of Texas at San Antonio, where he had been on the faculty for 22 years. Alan is now a staff scientist at Southwest Research Institute and focuses on quantitative analysis of deformation processes and stress in diverse tectonic regimes and conducts research and technical assistance projects for the oil industry.

Ronald McGinnis received his B.S. and M.S. degrees in geology from the University of Texas at San Antonio in 2002 and 2005, respectively. He is a senior research scientist at Southwest Research Institute. His work includes structural geological analysis of groundwater aquifers, characterization of faulted and fractured hydrocarbon reservoirs, and three-dimensional modeling of structurally complex hydrocarbon reservoirs and groundwater aquifers. In addition, he prepares and teaches training courses for the energy industry.

David Ferrill received his B.S. degree in geology from Georgia State University in 1984, his M.S. degree in geology from West Virginia University in 1987, and his Ph.D. in geology from the University of Alabama in 1991. He is a licensed professional geoscientist (geology) in the state of Texas. Before joining Southwest Research Institute in 1993, he was an exploration geologist at Shell Offshore Incorporated. David is now a director at Southwest Research Institute and performs geologic analyses, structural geologic consulting, and training for the oil and gas industry.

ABSTRACT

Faults are important components of hydrocarbon and other reservoirs; they can affect trapping of fluids, flow pathways, compartmentalization, production rates, and through these, production strategies and economic outcomes. Displacement gradients on faults are associated with off-fault deformation, which can be manifest as faulting, extension fracturing, or folding. In this work, displacement gradients—both in the slip direction and laterally—on a well-exposed large-displacement (seismic-scale) normal fault within the Balcones fault system of south-central Texas are correlated with anomalous deformation patterns adjacent to the fault. This anomalous deformation consists of two superimposed small-displacement fault systems, including (1) an earlier set that formed in response to a displacement gradient in the slip direction, and (2) a later set of oblique faults that formed in a perturbed stress-and-strain field in response to a lateral displacement gradient on the fault. Bed dip, fault-cutoff relationships, and small-displacement fault patterns in the adjacent rock volume inform strain and paleostress estimates. Results indicate that seismically resolvable displacement gradients on and bed dips adjacent to the seismic-scale fault provide a means by which the smaller (subseismic-scale and off-fault) deformation features can be predicted both in terms of orientation and intensity. Specifically, lateral displacement gradients on a normal fault with dip-slip displacement will generate fault-strike-parallel extension, causing anomalously oriented (in the far-field stress context) deformation features adjacent to the fault. Displacement gradient analysis can be used to help predict the characteristics of subseismic-scale deformation within a reservoir adjacent to a seismic-scale normal fault.